The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 06, 1990
Filed:
Jul. 05, 1988
Applicant:
Inventor:
Keiko Shimada, Tokyo, JP;
Assignee:
NEC Corporation, , JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
H04M / ; H04M / ;
U.S. Cl.
CPC ...
379389 ; 379390 ;
Abstract
A loudspeaker telephone has a circuit which is much less likely to go into singing or howling during the change over time while it is switching between transmit and receive modes. This is done by using FETs as variable resistors during the change over period. As a result of the resistance variation during change over, the total gain of both the transmit and receive channels added together does not exceed the gain during either the transmit or the receive modes.